// Copyright (C) 2024 Kumo inc.
// Author: Jeff.li lijippy@163.com
// All rights reserved.
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
//
#pragma once

#include <cstddef>                       // size_t

// Efficiently allocate fixed-size (small) objects addressable by identifiers
// in multi-threaded environment.
//
// Comparison with new/delete(glibc 2.3.4) under high contention:
//   -----------------------------
//   get<int>=26.1 return<int>=4.7
//   get<int>=46.1 return<int>=5.4
//   get<int>=27.5 return<int>=5.3
//   get<int>=24.8 return<int>=6.5
//   get<int>=26.6 return<int>=5.3
//   get<int>=24.7 return<int>=4.9
//   get<int>=67.8 return<int>=5.5
//   get<int>=36.7 return<int>=5.0
//   --------------------------------
//   new<int>=295.0 delete<int>=234.5
//   new<int>=299.2 delete<int>=359.7
//   new<int>=288.1 delete<int>=219.0
//   new<int>=298.6 delete<int>=428.0
//   new<int>=319.2 delete<int>=426.5
//   new<int>=293.9 delete<int>=651.8
//   new<int>=304.9 delete<int>=672.8
//   new<int>=170.6 delete<int>=292.8
//   --------------------------------

namespace turbo {

    // Specialize following classes to override default parameters for type T.
    //   namespace turbo {
    //     template <> struct ResourcePoolBlockMaxSize<Foo> {
    //       static const size_t value = 1024;
    //     };
    //   }

    // Memory is allocated in blocks, memory size of a block will not exceed:
    //   min(ResourcePoolBlockMaxSize<T>::value,
    //       ResourcePoolBlockMaxItem<T>::value * sizeof(T))
    template <typename T> struct ResourcePoolBlockMaxSize {
        static const size_t value = 64 * 1024; // bytes
    };
    template <typename T> struct ResourcePoolBlockMaxItem {
        static const size_t value = 256;
    };

    // Free objects of each thread are grouped into a chunk before they are merged
    // to the global list. Memory size of objects in one free chunk will not exceed:
    //   min(ResourcePoolFreeChunkMaxItem<T>::value(),
    //       ResourcePoolBlockMaxSize<T>::value,
    //       ResourcePoolBlockMaxItem<T>::value * sizeof(T))
    template <typename T> struct ResourcePoolFreeChunkMaxItem {
        static size_t value() { return 256; }
    };

    // ResourcePool calls this function on newly constructed objects. If this
    // function returns false, the object is destructed immediately and
    // get_resource() shall return nullptr. This is useful when the constructor
    // failed internally(namely ENOMEM).
    template <typename T> struct ResourcePoolValidator {
        static bool validate(const T*) { return true; }
    };

}  // namespace turbo

#include <turbo/memory/resource_pool_inl.h>

namespace turbo {

    // Get an object typed |T| and write its identifier into |id|.
    // The object should be cleared before usage.
    // NOTE: T must be default-constructible.
    template <typename T> inline T* get_resource(ResourceId<T>* id) {
        return ResourcePool<T>::singleton()->get_resource(id);
    }

    // Get an object whose constructor is T(arg1)
    template <typename T, typename A1>
    inline T* get_resource(ResourceId<T>* id, const A1& arg1) {
        return ResourcePool<T>::singleton()->get_resource(id, arg1);
    }

    // Get an object whose constructor is T(arg1, arg2)
    template <typename T, typename A1, typename A2>
    inline T* get_resource(ResourceId<T>* id, const A1& arg1, const A2& arg2) {
        return ResourcePool<T>::singleton()->get_resource(id, arg1, arg2);
    }

    // Return the object associated with identifier |id| back. The object is NOT
    // destructed and will be returned by later get_resource<T>. Similar with
    // free/delete, validity of the id is not checked, user shall not return a
    // not-yet-allocated or already-returned id otherwise behavior is undefined.
    // Returns 0 when successful, -1 otherwise.
    template <typename T> inline int return_resource(ResourceId<T> id) {
        return ResourcePool<T>::singleton()->return_resource(id);
    }

    // Get the object associated with the identifier |id|.
    // Returns nullptr if |id| was not allocated by get_resource<T> or
    // ResourcePool<T>::get_resource() of a variant before.
    // Addressing a free(returned to pool) identifier does not return nullptr.
    // NOTE: Calling this function before any other get_resource<T>/
    //       return_resource<T>/address<T>, even if the identifier is valid,
    //       may race with another thread calling clear_resources<T>.
    template <typename T> inline T* address_resource(ResourceId<T> id) {
        return ResourcePool<T>::address_resource(id);
    }

    // Reclaim all allocated resources typed T if caller is the last thread called
    // this function, otherwise do nothing. You rarely need to call this function
    // manually because it's called automatically when each thread quits.
    template <typename T> inline void clear_resources() {
        ResourcePool<T>::singleton()->clear_resources();
    }

    // Get description of resources typed T.
    // This function is possibly slow because it iterates internal structures.
    // Don't use it frequently like a "getter" function.
    template <typename T> ResourcePoolInfo describe_resources() {
        return ResourcePool<T>::singleton()->describe_resources();
    }

}  // namespace turbo
